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Tuesday, February 7, 2012

I had a folder full of MP3s. I wondered whether any of them were bad. In a brief previous search, I found MP3 Diags as a possible MP3 tester. This post describes what I found when I tried it out.

Trying Out MP3 Diags

I was using MP3 Diags 1.0.07. It had a Mac-type interface that I disliked. That is, instead of a menu with words that had meaning to me, it showed big, gaudy icons that mostly meant nothing until I hovered my mouse over them to get the tooltip. (The icons shrank to a more pleasant size when I shrank the program to fill only part of the screen.) The tooltips were visible only when MP3 Diags was in focus onscreen; I couldn't see them while I was typing these words.

With those initial reactions, I placed myself squarely among those who plunge into a program without first reading its documentation. I was admittedly more inclined toward the WFM philosophy than toward the RTFM philosophy. Windows programs did generally seem capable of using menus, including cautionary pop-ups, putting risky functionality into Advanced tabs, and otherwise steering stressed users into safe or pre-warned channels of behavior. I appreciated that the MP3 Diags programmer had provided many pages of documentation, among which he warned that the program was not really designed for those who were looking for a pushbutton solution. But it had to be clear that many users would never see that warning, or would perhaps mistakenly think they understood it when they did not, and that was the basis on which I approached the program.

After hovering over all of the icons, I chose two that seemed relevant for starting purposes. First, when I hovered my mouse over the gearlike icon at its top left corner, the tooltip said, "Scan folders for MP3 files [Ctrl+S]." From the Windows world, a gear icon would normally mean Tools; it seemed to me that a different icon would have been better, with a tooltip that said, "Select folders to scan." That option let me use checkboxes to designate a particular folder. The MP3s in that folder were not large; they averaged about 400K each. When I checked the boxes, the program was ready to begin scanning. I canceled out of the gear icon and went to the wrench-and-screwdriver icon, at the top right corner of the program, that seemed more fitting to its purpose: adjust settings.

Then I had to go back into the gear icon to run the program. On a fairly up-to-date computer, it seemed to diagnose about 12 MP3s per second. When it was done, it put up this notice:

Your files are not fully supported by the current version of MP3 Diags. The main reason for this is that the developer is aware of some MP3 features but doesn't have actual MP3 files to implement support for those features and test the code.

You can help improve MP3 Diags by making files with unsupported notes available to the developer. The preferred way to do this is to report an issue on the project's Issue Tracker at http://sourceforge.net/apps/mantisbt/mp3diags/, after checking if others made similar files available. To actually send the files, you can mail them to ciobi@inbox.com or put them on a file sharing site. It would be a good idea to make sure that you have the latest version of MP3 Diags.

You can identify unsupported notes by the blue color that is used for their labels.

At that point, the MP3 Diags screen consisted of three panes. In the top third of the screen, MP3 Diags listed the MP3s that it had tested, with columns indicating which Notes applied to them. In the middle third of the screen, MP3 Diags provided explanations of those notes. In the bottom third, MP3 Diags seemed to be showing me details about the single MP3 that was currently highlighted at the top. For instance, the bottom pane said this about one file:

That last pane didn't seem too important for present purposes, so I focused on the middle pane. It looked like MP3 Diags had found four kinds of things worth commenting on, in the files that I had submitted for diagnosis. None of these were error messages; they were all just informational. They read as follows:

fa - No ID3V2.3.0 tag found, although this is the most popular tag for storing song information.

ob - No supported tag found that is capable of storing song information.

ab - Low quality MPEG audio stream. (What is considered "low quality" can be changed in the configuration dialog, under "Quality thresholds".)

an - No normalization undo information found. The song is probably not normalized by MP3Gain or a similar program. As a result, it may sound too loud or too quiet when compared to songs from other albums.

(I was not able to copy and paste these messages from MP3 Diags, and therefore had to retype them here.) I didn't know where the letters (e.g., "fa") came from; I would have found it more helpful to see error codes grouped into areas of concern (e.g., quality, tags, playability). The point seemed to be that there were no problems with the MP3s per se, as distinct from their tags and their quality and their normalization: they would play without errors. That was my concern. These weren't songs, as MP3 Diags seemed to assume; they were just old recordings of speech, and as such did not need to be recorded at a high bitrate. I just wanted to know whether anything had gotten corrupted.

I had been reading that middle pane with its "File Info" button clicked. I clicked on its "All Notes" button instead. It showed me errors like these:

aa - Two MPEG audio streams found, but a file should have exactly one.

ac - No MPEG audio stream found.

These were obviously much more worrisome, and I didn't seem to have them, so that was good. Ah, but now that I focused on the top pane, I suspected that the four notes shown above (fa, ob, ab, and an) might apply only to the one MP3 that was highlighted in the top pane. Was I supposed to page down through all of the MP3s to do a manual check of which ones might have which errors? I tool-tipped the icons at the top of the screen again, looking for some kind of reporting function. I tried the "Filter by Notes" option. Unfortunately, since the error notes weren't grouped or hierarchically arranged under main topics (e.g., playability), it appeared that I would have to read all 23 notes and choose the ones that were worrisome -- as distinct from, say, just clicking on a main category and optionally selecting or deselecting subcategories. Some of the categories were presented in colored print, for unknown reasons. For instance, "aa" was brown, "an" was black, and "dj" was blue. The brown wasn't much different from the black; I had to look close to make sure. I wasn't entirely sure which categories to worry about: was "dj" ("Unsupported ID3V2 version") ominous, or did it just mean something to do with tags, which were irrelevant for purposes of these MP3s? I had to look at Wikipedia to see that ID3V2 related to information about the file, and apparently not its actual audio contents.

The error codes I chose to filter by were aa, ac, ad, ae, ak, bg, cb, ia, ib, ja, kb, kc, kd, and of. As that last example illustrates, it was awkward to write about some of these codes (e.g., an, of) without using quotation marks, since their letters formed English-language words. I wasn't sure, but a quick search suggested that these codes might be peculiar to MP3 Diags, and therefore easily changed, rather than being promulgated by some official MP3 authority.

Once I had selected those codes to filter by, the top pane in MP3 Diags changed. Now I could see that various files had various issues. It was also more obvious, now, that both the middle and bottom panes were providing information specifically about the file highlighted in the top pane. I would have liked to see a count of how many files had error "aa," for instance. Another useful feature would have been an option to display files in order of the nmber and/or seriousness of their errors, so that those with six or eight errors would come before those with just one. It would also have been interesting to see whether all of the files having a certain error were clustered in the same folder, in which case I would think maybe I should just replace that whole folder with good copies from a backup. I could refilter by folders, but apparently I couldn't filter, sort, or output a report by both folders and error codes. In fact, it seemed I couldn't output a report at all, which meant that I wouldn't be able to write a batch file to mass-delete or mass-zip any files that might be bad. If I selected a group of files in the top pane, it seemed that the only error codes I would see in the middle pane would be those pertaining to the first file in the group. There were no right-click options for selected files. And if I clicked on an error code column (e.g., ab), the program would not re-sort the files according to their values in that column.

Later, I would look in more detail at some of the error results (below). But at this point, MP3 Diags had helped me to clarify my thinking about Mac-like software. A while back, someone had asked me why I didn't just use Apple hardware and avoid the hassles I was experiencing with PC stuff. I had my reasons, but it was still a question worth keeping in mind. I knew I didn't really care for Macs, but hadn't thought much about why not, exactly. If MP3 Diags was any indication, it now seemed to me that one answer to that question would be that much Mac stuff is lacking in what would be considered basic functionality, among PC programs (although, as this post demonstrates, that's a problem in much PC software too). At its worst, Mac software seems to promote the idea that simplicity is superior. And it is, if you don't need to do anything complex. But again, that was just a passing reaction, based (at the moment) on one program that was surely not a fair representation of Mac software at its best.

It did seem quite possible that the programmer of MP3 Diags would find such remarks puzzling if not bizarre. I realized that my reactions could well be very far from his intentions. Again, my purpose was to convey a sense of how the program felt in use, a sort of walk-through from a new user's perspective. Another way to phrase the message was that idiosyncratic design may be best saved for those situations where it is really necessary.

Among all those programs, there didn't seem to have been much testing. Some were old and had not been updated. In most cases, the ratings at cites like CNET and Softpedia were based on just a few votes (sometimes just one). There were miscellaneous accounts -- for instance, MrSinatra reported questionable results from Audiotester. But I felt I was swimming in very murky waters. It seemed my best strategy might be to look at the ratings in Softpedia and CNET, supplemented by a search for reviews and a general sense of which of these tools had been most extensively used and recommended. Based on various comments I had seen, I decided to focus on MP3val, Checkmate, MP3Utility, MP3 Repair Tool, Foobar 2000, and Mr. Question Man.

Of those six programs, only Foobar2000 was listed on CNET (rated 4 out of 5 stars by 129 voters, excellent by editors). Softpedia listed MP3val (3.5 stars by 26 voters), Checkmate (3.0 stars by 24 users), MP3Utility (3.6 stars by 21 voters), Portable MP3 Repair Tool (2.7 stars by 30 users), Mr. Question Man (3.5 stars by 24 users) -- and Foobar2000 (4.6 stars by 1646 voters). I decided to start with Foobar2000. If that didn't lead where I wanted, I would try looking at MP3val, MP3Utility, and/or Mr. Question Man.

But then I ran another search. I was curious as to whether Winamp would provide at least the same functionality as Foobar2000. The search inadvertently pointed me toward two other MP3 checking programs, both on Softpedia, that looked like they might actually be more widely used than some listed in the previous paragraph. Those two programs were MP3-Check (3.8 stars by 63 voters) and MP3 Checker (3.9 stars, 25 users). As for Winamp itself, a couple of searches seemed to indicate that it did not share Foobar2000's ability to test MP3s. These results suggested that, if Foobar2000 didn't do the job, I should look next at MP3 Checker and MP3-Check, before turning to the others listed above.

Verifying MP3s in Foobar2000

I had expected Foobar2000 to give me a funky, multicolored player interface like Winamp. Instead, I got a straightforward space where files would be listed. I didn't see where it would have the ability to verify MP3s, so I went back to that old thread and saw that I would first have to load some files and then right-click on them and select the appropriate option. I did that. Loading files took a while. Foobar2000 indicated that it was "processing" them. It seemed to be handling only a few per second. When it was done, unfortunately, a right click revealed no testing options.

On the other hand, a right-click on an MP3 in Foobar2000 did present the possibility of doing a mass conversion. Foobar2000 offered ten output conversion formats, including WAV. (It also offered ways of modifying the output, e.g., crossfade, skip silence). This raised the possibility that I could do a mass conversion. Presumably a bad file would not be capable of being converted to another format.

Or at least a bad file would not produce good sound upon conversion. I visualized an MP3 testing program of the future. It would extract sound samples from several different points in the MP3, including beginning, middle, and end, and would compare them against designated reference files containing samples of the kinds of noise that the tested file should contain. Perhaps this imaginary program would concatenate copies of MP3s not fitting the profile, display the waveform, and underneath it show the name of the file, and the location within the file, from which the presently viewed sound sample was taken. That way, users could eyeball the program's judgments as to which MP3s were conforming or nonconforming, and could have some hands-on assurance that the program was accurately detecting acceptable vs. screwed-up MP3s.

I didn't have a program like that. But, as I say, I did have the option of doing a bulk conversion. Apparently Foobar2000 and, as it turned out, Winamp would do it. Cool Edit 2000 (no longer available) would do it, and so, probably, would some other audio editors. I was afraid that conversion could take a long time, but Foobar2000 converted a test group of 20 of these small MP3s within just a few seconds, and the files played successfully. So this was one possible route. I guessed that Foobar2000 would convert a blank file without objecting, though, and would otherwise fail to provide some of the warnings that I had seen in MP3 Diags (above). I decided to look at other possibilities.

MP3 Checker and MP3-Check

I looked at the Softpedia and CNET pages for Convivea's MP3 Checker. They essentially repeated what I saw on the MP3 Checker homepage. It sounded like a simple and capable program. The latest version was 1.08, released on July 22, 2006. I also looked at the homepage and the Softpedia and CNET pages for MP3-Check by AudioMoves. On this very preliminary basis, I was leaning toward MP3-Check over MP3 Checker because the MP3-Check homepage provided a more detailed description of what it did, and because its webpage and the product both seemed to have been updated within the past year or less.

So I downloaded MP3-Check 1.40 from Softpedia and installed it. It appeared to be designed primarily to check for MP3s that might have problems with quality or with their tags. These were not my concerns at present; I knew that some of the MP3s I would be testing might have bad or nonexistent tags, low bitrates, low sample rates, low volume, or might use joint stereo -- to cite the five criteria that MP3-Check allowed me to select and, to varying degrees, to adjust. I turned off all of those options except the tag check, which did not clearly appear capable of being turned off. I checked the option to Create Status Logfile. Then I ran the program on the same folder that I had tested with MP3 Diags (above). I could see indications in the program's status bar that it was checking files very quickly.

When MP3-Check was done, it put up a little notice indicating how many files it had checked. It calculated an average time of about 55ms per MP3, for these little MP3s that I had it check. When I clicked OK on that notice, it opened its logfile. The log showed me the names of the files it had checked, and their sample and bit rates. The log was tab delimited, so I could copy and paste directly into Excel and sort by the various columns (e.g., bitrate), to see if anything looked odd. There were several files with very low bitrates. I dug those out and listened to them. Two of them were corrupted, and I was able to replace them with backups. But those were the only bad files I was able to find this way. MP3-Check did indicate that a large number of my files had tag problems, as I expected. It also indicated that there was one "Unordinary MP3" in my list. I wasn't sure what was the matter with that file. It seemed to play OK. Otherwise, I was done with MP3-Check.

MP3-Check vs. MP3 Diags vs. Mr. Question Man

I wondered if MP3 Diags had detected the two or three bad files that I had just identified using MP3-Check. I hadn't closed MP3 Diags yet, so now I went back to look at the results it had shown me. Looking through those results was not easy. There was no Ctrl-F option to find a specific file by name. There was also no Ctrl-A option to select all files in the list. PgUp worked, but Home didn't, so I would have to page or scroll to get to the top of the list. Once I was there, there didn't seem to be any Shift-End or other key combination that would let me select the whole list that way either. I could select the whole list by starting at the top and doing a Shift-PgDn until I got to the bottom, or by scrolling all the way down, but of course this would take a long time with a large list. And what was the point? Once I had the whole list selected, Ctrl-C worked for only one item at a time, and there was also no right-click option, by which I could copy the list and paste it into a spreadsheet or Notepad for further searching and comparing. Worse, my attempts to highlight the whole list with Shift-PgDn caused MP3 Diags to freeze up. It came back to life after five or ten minutes, but this was not encouraging.

I thought maybe I could find those few bad files, if MP3 Diags had detected them, by narrowing my filter to just those categories that might have caught a corrupted file. But I thought I had already done that, when I decided to disregard tags and such (above) and focus instead on audio stream issues.

It seemed that MP3 Diags was a good start on a potentially great program. But I was uncomfortable with what seemed to be its core idea: never mind about the details; just click on the proper selection and we will take care of fixing your MP3s. It was a nice dream, and their colorful GUI seemed to support it, but so far the program had not won my confidence. I knew it was quite possible for a magical, black-box program to make things worse. I appreciated that these were all freeware programs, and that their creators had kindly made them available to the rest of us. It was just that I was looking for one really good program to do this job right and not make more headaches for me.

At some point in the process, I took a look at Mr. Question Man. Its webpage had not been active since 2006, and its description on Softpedia did not make clear whether it would repair MP3s, as distinct from merely providing information about them. But I went ahead with it anyway, on the strength of its positive user votes, few but mighty. It did turn out to be informational only. I appreciated its option for configuring the Isolinear Optical Chips Latency, on the Settings tab devoted to PapalaPapIHaveToCustomizeEverything. Funny program. I was thinking the writer should try political journalism. S/he might have a positive impact there.

MP3 Checker

I downloaded and ran MP3 Checker. It made a good initial impression, with practical options like "Do not report MP3s with minor glitches as BAD" and "Move MP3s with errors to the quarantine directory" (typos corrected here). I didn't like that I couldn't resize its window. And in the time it took me to write that last sentence, it had finished its scan of a rather substantial number of MP3s; it took the focus onscreen; and since I was in the middle of typing, my keystrokes seemed to be just what it needed to shut itself down. It was like a miniature tornado had ripped across my screen, kicking up a little dust but apparently not doing anything significant.

I started it up and ran it again. It had remembered all of my previous settings except the folder where I wanted it to look for MP3s. This time I made a point of finishing my typing before I started it, so I wouldn't inadvertently shut down its closing announcement again. What I saw this time -- again, after running for less than a minute -- was not good. It said that it had completed the scan and had scanned 0 files, processing 0 total bytes of data, verified 0 good MP3s, and detected 0 bad MP3s.

There had to be something wrong. A couple dozen users had given this thing fairly good marks. It had seen my MP3s -- I could see it listing their names in its status bar. It believed it was doing something with them. I was missing something somewhere. Maybe its users had been running Windows XP -- maybe somehow that made a difference? I had no idea. A discussion thread conveyed the impression that MP3 Checker was a casual project and seemed to produce erroneous results. With all due respect to other reviewers who liked it, I concluded that this was not the program for me.

MP3val

As noted above, several other MP3 validation tools had received ratings in the vicinity of 3.5 stars from a couple dozen users each. MP3val was one of those. It came with the executable file mp3val.exe, which would run from the command line with several options including -f (try to fix errors) and -si (suppress info messages). I chose to run it as a portable GUI program. There were virtually no settings options. Basically, I just pointed it to the folder containing the MP3s and told it to scan them. It loaded the list of files in that folder, and then gave me options of scanning or repairing all or selected files within that folder. I told it to scan them. It ran down the list in a spreadsheet-like layout with two columns: file name and state (i.e., condition). In a small pane at the bottom, it displayed what I guessed I would have seen if I had run the command-line version: the name of the file it was analyzing, a warning that the file contained no supported tags, and a statement of the file's properties (e.g., its number of frames, type of MPEG, number of tags, CBR). It was proceeding quickly but not instantly. It did appear to be doing a genuine scan.

When it was done, I tried to sort the list of files by clicking on the header of the State column. That didn't work. The procedure was, instead, to go into View > Scanned Files with Problems. It showed me a list of troubled MP3s. When I selected one, the pane at the bottom told me what the problem was. Here were some of the warnings displayed there:

MPEG stream error, resynchronized successfully.

No supported tags in the file.

VBR detected, but not VBR header is present. Seeking may not work properly.

It seems that file is truncated or there is garbage at the end of the file

The manual (a simple HTML file included in the portable folder) listed a number of other possible error messages. I would soon be comparing these error messages against those generated by MP3Utility (below).

The manual did not provide an indication of how I might save the scan results into a file. Ctrl-A didn't work, but I was able to select all of the files in the Problem list by using Ctrl-Shift-End from the top. But once they were selected, Ctrl-C didn't work to copy them, and a right-click just gave me options to delete, scan, or repair the selected files. I looked in vain for a log file that it might have created in its program folder; apparently its list of problem files was saved either in RAM or in a temporary directory somewhere. (It belatedly occurred to me that I could perhaps access a log to get the information I had been unable to extract from MP3 Diags, above, but it was not clear to me what its MP3Diags.dat files was trying to say, so for practical purposes that workaround didn't work.) It probably would have been possible to get the list of problem files from the screen, using a capture-and-OCR program like Aqua Deskperience (which I had bought) or JOCR or SysExporter, though that route would be painful with a long list of files. It would probably be possible, and surely easier, to use the command-line version of the program to get a list of files.

MP3Utility

As noted above, I had found two other MP3 validators that had averaged 3.5 stars or better from at least 20 users. These were MP3Utility and Mr. Question Man. The Softpedia page for MP3Utility, a portable, seemed to indicate that the program's last revision was in 2009. The webpage and, even more, its Readme.txt also provided an encouraging amount of detail. I got the impression of a careful, thoughtful effort to identify and handle flawed MP3s.

MP3Utility offered few but potentially useful options, such as the possibility of adding it to the right-click context menu. When I ran it on my test folder, it identified 16 bad MP3s, moved them to a designated folder, and allowed me to save its log file for later reference.

I took a look at those results. For 15 of those 16 bad MP3s, the logged error was of this type: "First sync error at approx.1:31 (80% through audio)." For the other one, the error was, "Can't locate first valid frame header within 5,000 bytes of beginning of file." The MP3Utility Readme said that the program would identify several kinds of errors, which I summarize as follows:

Unable to open file (file is protected by another application or was moved after being initially loaded into MP3Utility)

So the logged results of the search of my MP3s did not match up exactly with this list, but apparently the only errors in my MP3s were in the last category: I had 16 files with sync/header errors. The log stated that it had "found errors/warnings in 16 files," so evidently MP3Utility didn't think any of my files had any of the other errors listed here.

Comparison of Errors Found

How did the results from MP3Utility compare against the results of other programs? I had made a slight mistake, for comparison purposes: I had gone ahead and replaced two bad files after running MP3Check, as noted above. But otherwise the errors identified by MP3Utility should have matched up exactly with the errors identified by the other programs (above) that did produce a list of bad files. The programs of particular interest, at this point, were MP3 Diags, MP3-Check, and MP3val.

I looked at MP3 Diags first. I wondered how its relatively extensive list of "notes" would match up with the list of errors just given. It seemed that MP3Utility was superior on the first one, "Unable to open file," insofar as there was no acknowledgement of any such possible error in MP3 Diags. In other words, MP3 Diags would apparently give the user the impression that all files had been checked, even if some of them were locked or not found. This incorrect information may have seemed of no concern from the MP3 Diags perspective, since the program appeared to be oriented toward giving the user a complete (long) list of errors and then, after running a fix, presumably declaring most if not all of them to be repaired.

The second MP3Utility error, "file too short," appeared at first to be divided into at least three categories in the MP3 Diags errors: "no MPEG audio stream found" (which MP3 Diags labeled an "ac" type error), "invalid MPEG stream - fewer than 10 frames" (type "ak"), and "File contains null streams" (type "kd"). But possibly I had misunderstood what a "stream" was. I thought a stream was the audio data, as distinct from some sort of header and/or tailer that would contain non-audio data (e.g., tags). But it turned out that, at least in mp3HD format, you could have an MP3 that would have two data streams. Apparently that was not possible when MP3 Diags was created, else its programmer would not have included the "aa" error message, which stated that a file should have exactly one audio stream. Then again, some MP3 Diags error descriptions (e.g., "kc") did seem aware of this. Anyway, MP3 Diags identified a number of MP3s with these problems: many with an "ac" error, many with an "ak" error, and six with a "kd" error.

MP3 Diags did not provide a way to right-click or double-click on a file listed in its onscreen error report, so I searched manually to check some of the files listed under those three error categories. First, I noticed that three of the "kd" files were reported as having "ak" errors as well. These seemed to be exceptionally troubled MP3s. All three of these were in the folder containing Bad MP3s that MP3Utility had segregated. So, good, the programs seemed to agree about those. How about the "kd" files not containing "ak" errors? Those were in the Bad MP3s folder too. So MP3 Diags and MP3Utility seemed to agree that "kd" errors were bad (though possibly MP3Utility had moved one or more of those files to the Bad MP3s folder for some other reason). But obviously MP3Utility did not share the MP3 Diags concern with many other files, else the Bad MP3s folder would have contained far more than just 16 files. It did not appear that MP3 Diags was trying to produce a careful technical analysis that researchers and others could use for multiple purposes. If that had been the case, it would presumably have been possible to export the MP3 Diags error results to a log file. Fairly or not, I was reminded of those anti-malware programs that seemed to exaggerate the number and significance of threats to one's computer security. Spot checks of several other files containing both "ac" and "ak" (but not "kd") errors did not lead to any obvious problems: the files seemed to play OK.

As noted above, the next MP3Utility error, "Can't locate first frame header," was apparently serious enough to qualify a file as a Bad MP3. I couldn't tell which MP3 Diags error would be similar to this one. The only MP3 Diags errors that referred explicitly to headers were "bg" and "cb," but both of those were described as being issues that would matter only to "some players." The one Bad MP3 in which MP3Utility found this error was not included among those listed by MP3 Diags as having either "bg" or "cb" errors.

I decided not to examine the next two errors in the foregoing list of errors that MP3Utility would identify, since the Readme said those could probably be safely ignored. This took me to the last item in the list. The idea there seemed to be that MP3Utility had found a frame header, but it couldn't be read, and this caused or was related to a sync error, and that was serious. MP3 Diags did not have any error messages referring to "sync errors" per se.

Since I was not doing too well in an attempt to compare apples to apples, between MP3 Diags and MP3Utility, I decided to try another strategy. My idea was to filter the MP3 Diags output for those errors that sounded most serious, according to the MP3 Diags error descriptions, and then compare the results against the set of files that MP3Utility had moved to the Bad MP3s folder. But as I went down the MP3 Diags list, I couldn't really tell if any were serious. The one exception was "ac" ("No MPEG audio stream found") -- but as noted above, I had sampled some "ac" files and they played, so I didn't understand how MP3 Diags could say that it found no MPEG audio streams in them. I mean, they were MP3 files, and MP3 is a kind of MPEG. I tried renaming one of them as a WAV and playing that in IrfanView, and that produced an error ("Can't read file header"), and the error went away when I changed it back to an MP3 extension. It did seem to have an MPEG stream.

In a modification of that alternate strategy, I filtered the MP3 Diags list for all error messages that sounded like they could involve significant problems in playback (except for "kd," which I had already examined separately, above). The ones I selected were "aa," "ac," "ad," "ak," "bg," "cb," "ib," and "kc." MP3 Diags didn't give me a union/intersection choice -- that is, I couldn't indicate whether I wanted the program to display only those files that had *all* of these problems -- so instead it showed me all of the files that had *any* of these problems. And as noted earlier, MP3 Diags also didn't give me a way to sort this list according to the numbers or types of errors. I paged down through the list and manually selected a half-dozen files that had at least seven of these problems. They all played OK -- including a couple that MP3Utility had placed into the Bad MPGs folder.

My conclusion about MP3 Diags, at this point, was that -- for whatever reason -- it was displaying large numbers of error messages that didn't seem to have significance for purposes of playback (as distinct from, say, tag editing). In so doing, its very limited options meant that users would be at considerable risk of missing the potentially small number of files with real problems. As noted above, this could make sense for the user whose available time was commensurate with the number and length of files being checked, but it could be overwhelming for others.

Possibly users would eventually see the files with major problems, if they proceeded to let MP3 Diags repair their files. That is, maybe there would be only a few seriously troubled files left in the list, after the repair process ran. But I didn't want to let MP3 Diags have its way with my files if I didn't actually need to do that. After all, the problematic files seemed to be working OK, and these other programs weren't telling me that I needed repairs on large numbers of MP3s. So I didn't get to that stage of seeing what files would remain on the MP3 Diags list after it ran a repair.

Moving along, then, how about a comparison among MP3Utility, MP3-Check, and MP3val? As noted above, MP3-Check had identified only a couple of troubled files, and I had replaced them. I hadn't kept their names, but I had a backup of the tested folder, so I ran MP3-Check there. Ah, yes, now I remembered which files they were -- now that I was looking at them again. There were four of them. The MP3-Check log showed them as being recorded at the very low bitrate of 8kbps; and when I compared them against copies from an old backup, I could hear that there was something very wrong with them. And in part, maybe that was the point of programs like MP3 Diags -- maybe there were lots of little problems that you wouldn't notice. Maybe the file would sound like it was fine, until you compared it against another version, or played it with a different player. (The minimum bitrate threshold in MP3 Diags could not be set low enough to distinguish those 8kbps files from others recorded at 16kbps, which was a setting that some old or otherwise limited audio devices would use. That is, it was unlikely that those four files should have been stored at 8kbps, and my listening test had revealed that there was something wrong with them; but it was quite likely that I would have some files recorded at 16kbps.) I was listening to these files in IrfanView, which was able to play almost anything; maybe I would have been having a very different reaction if I'd had to use other software.

Anyway, I had to run MP3Utility and MP3val against that backup folder too, to get a good comparison among the three programs. The MP3Utility log showed me the same list of 16 bad files as before. It contained none of the four files that MP3-Check said were recorded at 8kbps -- files that I had manually confirmed were corrupted. MP3val gave me a far larger list of problem files, but it identified only one of those four. It seemed, then, that if I used either MP3Utility or MP3val, I might want to supplement it with a program, like MP3-Check, that would determine each file's bitrate.

Next, I compared the list of 16 problem files identified by MP3Utility against the larger list generated by MP3val. All were included in that larger list. I suspected that the remarks about the philosophy of MP3 errors, as laid out in the Readme for MP3Utility, might give me some guidance in adjusting the MP3Utility options, such that it would detect more errors -- possibly the very same ones as MP3val had identified. I was not feeling any particular need to look into this at present. It appeared that MP3val would do everything that MP3Utility would do, so I tentatively decided to go with MP3val.

The Conversion Alternative

As just noted, MP3val identified only one of the four low-bitrate files listed by MP3-Check. MP3val said that the problem with that file was, "This is a RIFF file, not MPEG stream." This gave me an idea. I checked a few of the other files in which MP3val had identified errors. The "no VBR header" problem seemed very common. It seemed that there might be advantages, for some purposes, in developing a concept of the ideal MP3 file -- what it would need to have in terms of tags and so forth -- and then building that into a bulk conversion process. Then all of the files would pass almost any test, assuming I disregarded inappropriate tests like the bitrate threshold, suitable for music but not text, found in MP3 Diags. In other words, I would run the conversion, and thereafter I would not have this motley collection of all sorts of errors, produced by various pieces of hardware. Maybe truly flawed files would stand out more obviously in that sort of arrangement.

I decided that the conversion approach was interesting but unnecessary at this point. It would perhaps be more appealing if, someday, I investigated the question of what standards were best for archival purposes. That is, there were probably people out there, somewhere, who had decided that 64kbps WMA was the most stable, durable, reliable format for long-term voice data archives. Or something like that. Standards and formats would change and become obsolete from time to time. Some such conversion might make sense, once I knew what I was doing. But for right now, there was no point doing a mass conversion to 56kbps, or some other number drawn from a hat.

Fixing the Problems

The MP3 Diags manual contained some advice: "If you like your files and they don't bother you, then you probably shouldn't change them." Such advice, seemingly reasonable, rested on the assumption, consistent with some aspects of that program's design and help system, that people would be using MP3 Diags to do detailed exploration of a limited number of individual music files that they would be listening to in their full length. Like most advice, unfortunately, there could be many situations to which it would not apply. One need only visualize a paralegal who was under time pressure to verify and sort dozens of multihour deposition recordings, or a corporate peon who was expected to clean up thousands of tech support call recordings, not to mention myriad casual users who had the belief, perhaps mistaken, that it was possible to have a trustworthy program that could identify and fix major errors in their song files. It seemed that users would be better protected by programs that used a standard design, so as to help them recognize when they were getting in too deep. As this post demonstrates, most users would probably find it prohibitively time-consuming to try to read the help files and master the eccentricities of various unfamiliar MP3 validation programs, in a search for one that did what they wanted. In other words, it could seem rather misanthropic to provide a big red "Fix" button along with a buried warning, "Never use the Fix button."

It presently appeared that MP3val had done a good if imperfect job of identifying problem files. Given its decent reputation (and the fact that I had a backup), I put the BAD MP3s (removed by MP3Utility) back into the main folder, along with the other MP3s, and told MP3val to scan that folder. When it was done, I told MP3val to repair all files. When that was done, I went into MP3val's View > Scanned Files with Problems. All of the bad files were reported as fixed. I spot-checked a few. They seemed to be fine.

I was surprised to see that, after MP3val ran, it still listed a number of files in the PROBLEM category. The problem, in every case, was that "no VBR header is present." Evidently this was something that MP3val could not fix. I thought that a conversion approach (above) might solve that sort of problem. There did not seem to be any urgency about it -- by this point, I was getting the sense that I had almost no MP3s that were absolutely unplayable and thus needed to be restored from a backup -- so I figured I could postpone repair of the "no VBR header" problem until I had learned more about archival formats (above).

I noticed, also, that MP3val had created .bak (backup) copies of the files that it had repaired. This was apparently the meaning of the Preferences > Delete backup files option: apparently MP3val worked by creating a backup file in the same folder as the MP3 file, making its changes, and then optionally deleting the backup.

Conclusion

I looked at a number of MP3 validation programs. I had limited time and expertise in which to do a comparison. I was able to eliminate some programs from consideration fairly easily. Others were closer to the mark, and deserved a more careful look. If I returned to this project in the future, I thought I might try to invest the time in reading the entire MP3 Diags help file and trying to get past its inflexible and alien interface.

For various reasons, MP3val presently seemed closest to what I needed. It was possibly overkill in the sense of identifying numerous problems, apparently minor, beyond the apparently more significant problems identified by MP3Utility. Even those more significant problems were not truly huge: the files seemed to play normally in IrfanView, both before and after I used MP3val to fix them. As far as I could tell, MP3 Diags was very much overkill, in the sense of identifying numerous problems that the help file then advised me to ignore, as long as my files were playing correctly.

MP3val and others did not draw my attention to a few files that had somehow gotten corrupted into a lower bitrate -- or something. I was not sure what had happened to those files, but I could see and hear that they had lost quality compared to old backup copies. MP3-Check provided bitrate information that I was able to copy and paste into a spreadsheet, where I could sort by bitrate to highlight such potentially problematic files. There may have been a faster approach to this particular issue through an MP3 player/information program like Foobar2000.

Foobar2000, Winamp, and some audio editors were capable of doing batch conversions of large numbers of files. If I did return to this project at some point, I thought it might be worthwhile to see if I could use a conversion program to fill in missing tags, homogenize bitrates, and otherwise convert these MP3s, created on different pieces of hardware, into a single, consistent format that would eliminate most if not all errors. I would probably use MP3 Diags, MP3val, MP3-Check, and/or some other informational program to guide me in arriving at the ideal form for such a conversion.

I felt that it would probably make sense to postpone that conversion inquiry until some future point when I would investigate archival formats. That is, I knew that formats were capable of becoming extinct, and I suspected that there was probably research and perhaps a consensus on what filetype, bitrate, and other characteristics were most likely to be supported into the indefinite future. Ideally, I would be able too do just one conversion, check it with just one capable MP3 checker by that point, and put such concerns to rest.

The interface is nothing macintosh-like. It is a FLOSS Single-Programmer's frontend; the original developer knows by memory the letter codes and icons and workflow, so they don't need to change. Macintosh users will hate seeing hexadecimal code. The icons are KDE-like, but the rest looks like old Java programs.

It seems extensive and powerful, and I will learn it, but I think I'd destroy files using it now.

A later post describes some steps for testing WAVs that may also be useful for testing MP3s. That post used one Boxoft freeware program, but Boxoft offered many others, probably including an MP3 converter.